In a case where in communication that uses a packet, a size of data that is transmitted exceeds a size suitable for containing the data in one packet, the data is divided into a plurality of pieces of data and the plurality of pieces of data are transmitted in state of being contained in a plurality of packets, respectively. Each of the plurality of packets that contain the plurality of pieces of data, respectively, that result from the division, contains a value common to every data, information indicating the order of packets, and information indicating whether or not a packet is a final packet (for example, Japanese Laid-open Patent Publication No. 10-341247).
Furthermore, in a case where data is divided into a plurality of pieces of data and the plurality of pieces of data are transmitted in a state of being contained in a plurality of packets, respectively, a transmission node that transmits a packet adds acknowledgement information for acknowledging normal reception in a reception node that receives the packet, to each packet, and transmits the packet containing the acknowledgement information. The reception node acknowledges whether or not the packet is normally received, based on the acknowledgment information (for example, Japanese Laid-open Patent Publication No. 2001-202345).
On the other hand, in a case where the packet is transferred via a plurality of paths, a flag that identifies a transfer that uses an in-order scheme which guarantees the order in which the packets arrive and transfer that uses an out-order scheme which does not guarantee the order in which the packets arrive, is added to the packet, and thus, communication that uses the in-order scheme and the out-of-order scheme is possibly performed. For example, in the communication that uses the in-order scheme, the packet is transmitted with a sequence number being sequentially incremented, and in the communication that uses the out-of-order scheme, the packet is transmitted with the sequence number being fixed (for example, U.S. Pat. No. 6,493,343).